Mann’s hockey stick disappears – and CRU’s Briffa helps make the MWP live again by pointing out bias in the data | Watts Up With That?

I have written exentensivley on the controversy over whether man is causing global warming/climate change or whatever you want to call it. You can go to my book Choosing the Red Pill and check out an entire chapter on ithere. The article that is linked below is a huge and massive story. That is because it was Michael Mann’s discredited hockey stick model (used shamelessly by Al Gore in his movie) that gave credence to the idea that it was man that was causing the climate to change rather than current warming being a result of a natural cyclical process. Without that famous “spike” (the blade of the hockey stick) recent warming does not appear to be alarming at all when viewed historically. That one of the original CRU and IPCC lead scientists has debunked the Mann chart is yet further proof that the “science” is not settled:

Shock, awe. Untruncated and unspliced data used in a new paper from Briffa and Melvin at UEA restores the Medieval Warm Period while at the same time disappears Mann’s hockey stick. Here’s figure 5 that tells the story:

Figure 5. Temperature reconstructions created using the 650-tree (‘alltrw’ data) TRW chronology (a) and the 130 tree (‘S88G1112’ data) MXD chronology (b). Chronologies were created using two RCS curves and were regressed against the Bottenviken mean May–August monthly temperature over the period 1860 to 2006. The shaded areas show two standard errors (see SI15, available online, for details) plotted either side of the mean where standard errors were scaled to fit the temperature reconstruction. The TRW and MXD temperature reconstructions of (a) and (b) are compared in (c) after they were normalised over the common period 600 to 2008 and smoothed with a 10 year spline. The lower two panels compare the reconstructions using the TRW chronology (d) and MXD chronology (e) with the mean of May to August monthly temperature from Bottenviken over the period 1860 to 2006.

Look at graph 5c, and you’ll see 20th century warmth matches peaks either side of the year 1000, and that for the TRW chronology 20th century warmth is less than the spike around 1750. This puts 20th century (up to 2006 actually) warmth in the category of just another blip. There’s no obvious hockey stick, and the MWP returns, though approximately equal to 20th century warmth rather than being warmer.

Whoo boy, I suspect this paper will be called in the Mann -vs- Steyn trial (if it ever makes it that far; the judge may throw it out because the legal pleading makes a false claim by Mann). What is most curious here is that it was Briffa (in the Climategate emails) who was arguing that some claims about his post 1960 MXD series data as used in other papers might not be valid. It set the stage for “Mikes Nature trick” and “hide the decline“. Steve McIntyre wrote about it all the way back in 2005:

Post-1960 values of the Briffa MXD series are deleted from the IPCC TAR multiproxy spaghetti graph. These values trend downward in the original citation (Briffa [2000], see Figure 5), where post-1960 values are shown. The effect of deleting the post-1960 values of the Briffa MXD series is to make the reconstructions more “similar”. The truncation is not documented in IPCC TAR.

I have to wonder if this is some sort of attempt to “come clean” on the issue. Mann must be furious at the timing. There’s no hint of a hockey stick, and no need to splice on the instrumental surface temperature record or play “hide the decline” tricks with this data.